The present invention relates generally to rotary mechanical fluid couplers, and more particularly to a multiple passage fluid coupler in which multiple fluids may be separately transferred to a workpiece through a combination non-rotating coupler member and a rotating coupler member.
For years, bearing-type fluid couplers have been utilized in coolant machining operations as an interface between non-rotating coolant supply hoses and rotating tool machine spindles. A typical bearing-type coupler includes a rotatable spindle adaptor having a co-axial fluid passage and a generally non-rotatable piston member having a co-axial fluid passage communicating with the adaptor fluid passage. Both components are assembled in concentric relation in a common housing. The piston and spindle adaptor are axially biased towards one another such that opposing faces of each component abut one another, thereby defining a seal interface. A mechanical seal placed around this interface forms a fluid-tight coupling of the two components. The spindle adaptor is typically supported by and journalled on coupler bearings at a first end proximate with the seal interface for rotation and is typically threadably connected to, and rotatable with, a machine spindle at its second end.
Regardless of the quality of machine tooling, the machine spindle, or the particular manufacturing process implemented, overall system quality level in the machining industry is typically affected by this bearing-type coupler for several reasons. First, today's machining industry requirements often dictate that machining operations be performed at relatively high speeds, typically at 4,000 rpm or higher. In addition, present machining operations typically require frequent machine stops and starts. Bearing-type couplers, while having satisfactory performance characteristics at speeds of around 2,500 rpm and while operating without frequent starts and stops, typically malfunction under the aforementioned more demanding conditions. Such malfunction typically is a result of rapid wear of the coupler bearings and the subsequent failure of the bearings due to overheating resulting from these conditions.
Second, present machining operations often require that fluids other than coolants be supplied to the tooling machines. Mechanical seals typically isolate bearings in bearing-type couplers from these fluids. However, these seals occasionally fail after long periods of use, thereby allowing fluid to leak into the coupler bearing housing. When exposed to these fluids, the coupler bearings often fail, thus resulting in the expense of coupler replacement and associated costs dues to machine down time.
Third, conventional bearing-type couplers often are connected to machine spindles in an unsupported manner, as typically there are no mounting support brackets associated with these couplers. As a result, a significant load is placed on the spindle. This load typically induces vibrations, which are often transmitted to the spindle bearing. Such vibrations decrease the life of the spindle bearing, the coupler bearings, and often affect machining accuracy, resulting in machined parts that do not meet spec. In addition, such induced vibrations often result in damaging and/or breaking of the cutting tool. Further, the induced vibrations significantly decrease the life of the coupler itself by accelerating bearing coupler wear and failure rates.
Fourth, coupler bearings incorporated within bearing-type couplers increase maintenance costs, as the bearings must be periodically lubricated. If the bearing couplers are not properly lubricated, bearing wear is significantly increased. As the bearings become worn, vibrations are induced, resulting in the above-mentioned problems.
In the past, several modifications have been introduced into machining systems in an attempt to minimize the above-mentioned limitations induced by bearing couplers. Such modifications have included the installation of swallow-type spindles, adapters, or dual coolant circuits into the machining operations in an attempt to reduce coupler induced vibration and in order to prolong the life of the coupler itself. However, such modifications have exhibited limited effectiveness and have added expense to the overall machining operation.
Subsequently, the introduction of bearingless couplers into the above-mentioned high speed, high pressure coolant machining operations has allowed many of the above-mentioned drawbacks associated with bearing couplers to be overcome. Such a bearingless coupler is disclosed in U.S. Pat. No. 5,174,614 entitled "Bearingless Rotary Mechanical Fluid Coupling", issued Dec. 29, 1992 to Kaleniecki, assigned to the assignee of the present application, and incorporated by reference herein. Such a bearingless coupler functions under operating conditions that would severely limit the life of a bearing-type coupler. In particular, the bearingless coupler is not affected by frequent spindle starts and stops, and can function at significantly higher spindle speeds. Also, the bearingless coupler is not affected when liquids other than coolants are passed through the spindle, as no coupler bearings, and thus no mechanical bearing seals are present. Further, a bearingless coupler such as that disclosed in assignee's aforementioned patent is bracket mounted, thereby minimizing the load placed on the tool spindle and thereby damping, and thus minimizing, vibrations transmitted from the coupler to the spindle. As a result, higher quality parts can be manufactured and damage to cutting tools and tool spindles is minimized. Additionally, system cost is reduced, as such a bearingless coupler is relatively maintenance free, thereby minimizing system down time.
While the assignee's aforementioned patent exhibits superior results when compared to bearing-type couplers, there is still a need for further advancement in the art. In particular, today's increasingly demanding machining requirements often require that two or more discrete quantities of coolants or other types of fluids be supplied to the machining operation simultaneously. While the aforementioned single passage bearingless coupler exhibits superior performance characteristics, there is thus a need in the art for a multi-passage bearingless fluid coupler that is capable of supplying two or more discrete quantities of fluids simultaneously to a tooling machine.
There is a further need for a multi-passage bearingless fluid coupler that may be adapted to fit any of a number of particular types of coupler requirements.
Thus, there is a need for a bearingless fluid coupler that exhibits all of the superior performance characteristics of the assignee's aforementioned patented bearingless coupler, while in addition being capable of supplying two or more discrete quantities of fluids simultaneously to a cutting tool.